This invention is generally directed to an electrophotographic imaging device containing certain cross-linked siloxy polymers, and more specifically the present invention is directed to cross-linked siloxy polymer release materials, and photoresponsive devices, especially overcoated layered devices, containing such materials, which release materials allow the achievement of excellent release and transfer of toner images from such devices.
The formation and development of images utilizing photoresponsive devices is well known, one of the most widely used processes being xerography as described in U.S. Pat. No. 2,297,691. In these processes the electrostatic latent image is developed by applying toner particles thereto, and subsequently such developed image is transferred to a permanent substrate such as paper. Development can be accomplished by a number of various known techniques including cascade development, powder cloud development, magnetic brush development, liquid development, and the like.
Recently there has been developed for use in xerographic imaging systems, and for use in imaging systems utilizing a double charging process as explained hereinafter, overcoated organic imaging members including layered organic and layered inorganic photoresponsive devices. In one such photoreceptor device there is employed a substrate, overcoated with a hole injecting layer, which in turn is overcoated with a hole transport layer, followed by an overcoating of a hole generating layer, and an insulating organic resin overcoating as a top coating. These devices have been found to be very useful in various imaging systems, and have the advantage that high quality images are obtained, with the overcoating acting primarily as a protectant. The details of this type of overcoated photoreceptor are fully disclosed in U.S. Pat. No. 4,251,612, on Dielectric Overcoated Photoresponsive Imaging Member and Imaging Method, J. Y. C. Chu and S. Tutihasi, the disclosure of which is totally incorporated herein by reference.
In one preferred method of operation as described in the aforementioned patent, the photoreceptive member is charged a first time with electrostatic charges of negative charge polarity, subsequently charged a second time with electrostatic charges of a positive polarity, for the purpose of substantially neutralizing the charges residing on the electrically insulating surface of the member, followed by exposing the member to an imagewise pattern of activating electromagnetic radiation, thereby forming an electrostatic latent image. The image can then be developed to form a visible image, which is a transferred to a receiving member. The photoresponsive device may subsequently be reused to form additional reproductions after erasure and cleaning are accomplished.
When employing certain overcoated organic photoreceptors in an imaging system various problems have been encountered with regard to the development and transfer of the resulting developed image. Thus, for example, the toner materials do not release sufficiently from the photoresponsive surface leaving unwanted toner particles thereon, causing such particles to be subsequently embedded into, or transferred from the imaging surface in later imaging steps, thereby resulting in undesirable images of low quality and/or high background. Also in some instances the dry toner particles adhere to the imaging member in print background areas due to the adhesive attraction of the toner particles to the photoreceptor surface. This can be particularly troublesome when silicone resins, or elastomeric polymers are employed as overcoat materials for their melted toner release characteristics. Low molecular weight silicone components can migrate to the surface of the silicone polymer layer and act as an adhesive toward dry toner particles brought in contact therewith during the image development step in the imaging process, such as in the xerographic imaging process. There thus results undesirable high background prints, since the toner particles, along with the toner image, are efficiently transferred to the receiving sheet when simultaneous transfer and fixing is thermally accomplished.